As one example of a working vehicle provided with such a hydraulic traveling device, a skid steering loader (for example, see Patent Document 1) in which the traveling devices having tires or crawlers are installed on right and left sides of a vehicle main body has been proposed. In the skid steering loader, making a turn in the proceeding direction is carried out by differentiating the operating speeds of the tires or crawlers by the traveling devices on the right and left sides. In general, the skid steering loader has a structure in which an engine for driving the traveling devices or the like is installed on a rear portion of the vehicle main body and by using the engine driving force, the traveling devices are driven to travel. In this case, as the traveling device, a hydraulic transmission (HST(Hydro-Static Transmission)), which drives a hydraulic pump by an engine and by using a hydraulic motor that is driven by receiving a discharged oil supply from the hydraulic pump, the tires or crawlers are driven to travel, has been used.
In the HST, the hydraulic pump of a variable capacity type is used, and the traveling speed control is carried out by controlling the variable capacity of the hydraulic pump. In this case, the variable capacity control of the hydraulic pump is carried out by using a discharged hydraulic pressure (charged hydraulic pressure) of the charge pump driven by the engine. In the case when, while a working vehicle is allowed to travel by the traveling device using the HST, the engine load is increased by an increase in the traveling load, the engine rotation is lowered, with the result that the discharge amount of the charge pump is also lowered. When the charged hydraulic pressure is lowered, the variable discharge capacity of the hydraulic pump that is controlled by the charged hydraulic pressure is lowered so that the engine load is reduced so as to prevent engine stalling.